THE  DETERMINATION  OF  LACTOSE  IN 

MILK 


BY 

GEORGE  CHARLES  EBERT 


THESIS 

FOR  THE 


DEGREE  OF  BACHELOR  OF  SCIENCE 


CHEMISTRY 


COLLEGE  OF  LIBERAL  ARTS  AND  SCIENCES 


UNIVERSITY  OF  ILLINOIS 


1922 


Finley 


(T> 


3 


iSt'L 


UNIVERSITY  OF  ILLINOIS 


192 


THIS  IS  TO  CERTIFY  THAT  THE  THESIS  PREPARED  UNDER  MY  SUPERVISION  BY 


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DEGREE  OF 


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Digitized  by  the  Internet  Archive 
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https://archive.org/details/determinationoflOOeber 


AGElIOwXEDGLIEllIT 


This  inYestigation  was  unde rt alien  upon 
the  suggestion  and  under  the  supervision  of  Dr. 
Duane  T.  Snglis,  to  whom  the  author  owes  bis 
sincere  apiDreciation  for  the  helpful  suggestions 
and  encouragament  given  as  the  worli  progressed. 


- THE  HETSRI.:ilTATI011  CP  lAOTCCE  IIT  IHXK  - 


Introduction  and  History 

Tha  inportanca  of  determining  milk  sugar  or  lactose  in 
nilk  analysis  was  recognized  as  far  kack  as  1876.  In  tha  de- 
conpcsition  of  milk,  lactose  suffers  a change  and  so  causes  a 
decrease  in  amount  of  total  solids  present,  Tha  lactose  is 
transformed  to  lactic  acid  thus  causing  discrepancies  in  analysis 
of  stale  milks, 

I,Iilk  is  one  of  the  important  articles  of  human  diet 
aied  So  should  not  ha  allowed  to  ha  adulterated.  A proper  stan- 
dard for  the  quality  of  cow*s  milk  should  he  acceptad. 

There  has  haan  ciuita  a large  amount  of  work  done  on 
tha  determination  of  lactose  hy  volumetric,  gravimetric  and  op- 
tical methods,  some  of  which  will  ha  here  outlined. 

In  1880  Huter  f^inalyst  5:35j  answers  two  (luesticns  that 
had  often  haen  asked  about  lactose  da tem'-inations  and  which  are 
answered  differently  hy  different  T^-orkers,  They  are,  first, 
what  is  tha  hast  method  for  an  analyst  to  follow  and  secondly, 
given  such  a method,  what  is  tha  true  acj.iiivalent  for  calculation 
of  results?  After  q.uite  extensive  work  Huter  concludes  that  tha 
hesi/  iDrocass  for  general  use  is  the  gravimetric  method  and  that 
it  should  ha  carried  out  according  to  strict  rules  so  as  to  en- 
sure a constant  equivalent  and  that  tha  precipitate  may  ha 
weighed  directly  as  cuprous  oxide  fCug^c). 

f 

Soma  workers  have  contended  that  tha  volumetric  process 
in  which  a small  amount  of  sugar  solution  is  brought  into  contact 


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with  strong  a-lkali  until  an  and  point  is  raachad,  is  tha  most 
rapid,  iluter  thought  and  the  same  theory  has  hean  held  hy 
others,  that  tha  volurnatriG  method  never  gives  really  accurate 
results  except  hy  accident.  A truly  constant  equivalent  cannot 
“be  ensured  unless  the  whole  can  he  diluted  to  such  a point  as  to 
render  the  alliali  harmless,  while  the  Cablings  solution  is  at 
once  added  in  sufficient  quantity  to  ins tantsjiecusly  perform  tha 
entire  reaction.  Both  tha  sugar  solution  and  the  Fahlings  solu- 
tion should  he  boiling  when  mixed  and  these  points  cannot  ha  ob- 
tained except  by  the  gravimetric  method. 

It  is  held  by  some  that  cuprous  oxide  is  not  stable  and 
should  be  converted  to  the  cupric  state  before  weighing.  The 
cuprous  oxide  should  be  precipitated  from  a boiling  solution  and 
washed  with  boiling  water  so  as  not  to  allow  long  e:cpoEura  to  tha 
air.  If  than  two  drops  of  petroleum  ether  are  placed  on  tha  pre- 
cipitate and  the  crucible  placed  in  a good  close  drying  chamber 
at  temperature  of  boiling  water,  the  cuprous  oxide  is  a more  con- 
venient and  accurate  article  for  weighing  than  the  varj-  hygros- 
copic cupric  oxide. 

I'iuter  found  by  accurate  checking  that  the  true  equival- 
ent is  146.3  parts  of  cuprous  oxide  to  every  100  parts  of  lactose, 
providing  the  precipitate  is  not  allowed  to  stand  in  the  solution 
for  any  length  of  time. 

In  1884,  E.  E.  Eiley  (Aualyst  IS:  174;  ihin.  Cham.  Jour. 

6;  S89)  Chemist  of  the  Enited  States  Department  of  Agriculture  anc. 
later  head  of  the  Bureau  of  Chemistry,  published  a vary  good  work 
on  the  specific  rotation  of  milk  sugar  and  tha  classification  of 

■,71ien  crystalline  milk  sugar  is  first 


milk  for  polarisation. 


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clissclvad  it  giv0S  a higher  rotatcrj^  power  than  it  had  in  the 
milk  frcn  which  it  wac  derived.  After  standing  for  12  - 20  hours 
or  immediately  on  hoiling  this  omtra  rotation  is  lost.  The 
various  values  published  for  the  specific  rotatory  power  of  lac- 
tose always  refer  to  the  constant  rotatory  power  and  not  the 
variable.  After  thorough  investigation,  T7iley  accepted  the 
value  obtained  by  Schiaoager,  as  = 52.53^  for  sxoocific  rota- 
tion of  lactose.  This  figure  has  stood  the  test  as  it  is  the 
value  generally  used  to  the  i^rasent  daj*. 

In  order  to  ha-ve  an  optical  method  which  is  satisfactoiy 
soma  means  of  clarifying  the  milk  solution  must  be  worked  out. 

All  of  the  albumens  and  other  laevo-rotatcry  compounds  must  be 
removed  from  the  milk,  leaving  a clear  colorless  filtra.te,  before 
polarisation  can  be  carried  out.  As  clarifiers  TTilej/'  used:  - 

1)  Saturated  solution  of  basic  lead  acetate,  sp.gr.  1.97. 

2)  nitric  acid  solution  of  mercuric  nitrate  diluted  with 
an  aoual  volume  of  water. 

3)  Acetic  acid,  sp.gr.  1.04,  containing  29^b  acetic  acid. 

4}  nitric  acid,  sp.gr.  1.197  containing  30^a  nitric  acid. 

5}  Sulphuric  acid,  sp.gr.  1.255  containing  30^  sulxohuric 

acid. 

6)  Saturated  solution  llaCl. 

7)  Saturated  solution  IlgSCA* 

8)  Solution  of  mercuric  iodide  in  acetic  acid;  formula: - 
ILl  33.2  grams;  HgOl  13.5  grams;  strong  acetic  acid  20  cc.  ; 
water  640  cc. 

Tliley  also  used  other  agents  for  clarifying,  as  solutions  of  min- 


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aral  salts  such  as  copper  sulfata,  and  hydrochloric  and  other 
acids.  The  last  he  did  not  deem  of  any  use  what  aver.  Acids 
and  alkalies  seem  to  increase  the  rotating  power.  He  showed 
that  any  great  excess  of  "basic  lead  acetate  caused  a considera"ble 
decrease  in  rotatory  poY/er.  It  is  not  clear  whether  this 
decrease  is  due  to  solution  of  the  alhurnens  or  precipitation  of 
the  sugar.  It  seams  to  make  very  little  difference  if  the  pre- 
Gip)itation  is  carried  out  in  the  hot  or  cold  "but  the  readings  of 
the  polariscopa  must  "be  taken  at  SO^G.  By  ccm"busticn  with  soda- 
lime  the  quantity  of  laevo-rotatory  matter,  calculated  as  nitro- 
gen, remaining  in  the  filtrate  after  treatment  with  "basic  lead 
acetate  is  much  greater  than  that  left  after  treatment  with  mer- 
curic iodide.  This  eirplains  the  higher  results  o"b tanned  when 
using  the  mercury  salts  and  shows  that  the  "basic  lead  method 
should  "be  a"bandcned  as  a method  of  clarification.  Hiley  decided 
that  the  "best  clarifying  agents  were  1 cc.  acid  mercuric  nitrate 
for  50  cc.  milk;  or  else  25  - 30  oc.  mercuric  iodide  for  60  cc. 
milk.  An  excess  of  the  mercuric  salts  does  no  harm  and  the  pre- 
cipitation may  easily  "be  carried  out  in  the  cold.  In  all  cases 
Hiley  allowed  2 cc.  for  50  cc.  milk  for  volume  of  precipitated 
casein. 

In  1895  A.  Hynther  Blyth,  (Analyst  20:  l2l)  v;crking  on 
the  estimation  of  car"bohydrates  in  milk,  admits  that  Br.  Hiley*s 
method  of  clarification  By  mercuric  nitrate  or  iodide  is  a very 
good  one.  However,  he  o"bjects  to  the  procedure  on  the  groumds 
that  the  solutions  cannot  then  "be  used  for  o.ny  other  purpose  than 
polarime trical  o"bservations.  That  is,  no  other  determinations 
can  "be  made  on  this  solution.  If  a shadow  instrument  is  used  an 


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almost  clear  whey  can  "be  obtained,  by  precipitation  with  copper 
sulfate  and.  if  the  proper  amount  is  used  the  filtrate  is  so  pale 
a blue  as  not  to  interfere  with  the  reading.  HLyth  seems  to 
have  been  the  first  investigator  to  attempt  this.  This  solution 
can  then  also  be  treated  with  Pehlings  solution  and  the  regular 
copper  reduction  method  followed  gravimetric ally. 

The  method  of  clarification  finally  adopted  by  Hyth 
for  precipitating  the  casein  was  by  acetic  acid.  S5cc.  of  milk 
was  diluted  to  about  50  cc.  with  distilled  water  and  then  strong 
acetic  acid  added  drop  by  drop  until  the  casein  begins  to  separ- 
ate. The  liquid  is  then  heated  to  boiling  and  whirled  in  a 
centrifugal  machine.  The  casein,  albumen,  coagulated  serum  and 
fat  are  collected  at  the  bottom,  while  the  supernatant  fluid  is 
easily  filtered.  The  precipitate  is  washed,  the  filtrate  cooled 
and  made  up  to  100  cc.  This  solution  can  then  either  be  polar- 
ized or  have  a copper  reduction  da termination  run  on  it.  The 
filtrate  is  usually  of  a feeble  yellow  color,  but  perfectlj/ 
bright  and  suitable  for  testing  for  substances  such  a.s  salicj’-lic 
acid,  borax,  dextrin  or  any  soluble  addition. 

Bliley  in  conjunction  with  Swell  in  1896  (;malyst  Si: 

18S)  worked  out  a method  of  determining  lactose  by  double  dilutior 
and  subsequent  polarization.  The  figure  formerly  accepted  by 
T7iley  for  the  volume  of  precipitate,  as  S ce.  for  50  cc.  of  milk, 
was  thought  to  be  somewhat  in  error.  To  overcome  this  error 
these  two  investigators  worked  out  the  following  double  dilution 
method.  The  clarifying  agent  used  was  acid  mercuric  nitrate, 
and  the  polarization  was  carried  out  in  a triple -field  shadow 
polariscope  of  the  Schmidt  and  Haensch  type  by  which  readings 


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accurate  to  .05  of  one  percent  mojr  i)e  taken.  The  flasks  used 
were  100  and  SOO  cc.  carefully  calilirated.  The  same  amount  of 
milk,  that  is  double  the  normal  weight  for  the  instrur.ient,  was 
used  in  each  flask,  clarified  and  polarized.  xill  readings  were 
made  in  duplicate  by  both  Vv'orkers  in  a 400  mm.  tube  in  order  to 
gat  the  most  accurate  results.  The  temperature  of  the  working 
room  was  kept  at  about  S0°C.  since  the  rotation  of  lactose  in- 
creases notabljT-  with  rise  in  temperature. 

By  means  of  the  following  algebraic  equations  ITiley  and 
Ewell  work  out  the  correct  volume  of  the  precipitate  and  the 
correct  reading  of  the  polarisccpe: 

let  x=  voluTiia  of  precipitate 
y=  correct  reading 
a=  reading  from  the  small  flask 
b = reading  from  the  large  flask 
Then,  SOO — x : 100  — x ; : a : b 
SOO  b — bx=  100  a— ax 


(1) 


X — a — b 


100  (a— S b) 


correct  volume  of  precipitate 


100  —X  ; 100  : : y : a 


: 100  : : y ; a 


y = a- 


a(a  — 3b) 
a — b 


(2) 


a^—  ab  — a^-4-  2ab 

5^=  a”-=-^5 


correct  reading. 


Rule  (3)  stated  in  words  is  that  the  true  polarization  as  deter- 
mined by  double  dilution  is  found  by  dividing  the  product  of  the 


7 


t\7o  readings  in  the  large  and  small  flasks  their  difference. 

According  to  7iley  end  lUn'all  this  method  ta}:es  vary 
little  more  time  than  a single  polarisation  and  should  he  used  at 
all  times  when  an  accurate  determination  is  to  he  made,  instead  of 
correcting  for  the  volume  of  precipitate  hy  any  arbitrary  factor. 

- In  1913  there  appeared  an  article  hy  TTalker  and  Aarsh, 

( J.  A.  0.  S.  35:  8S3]  in  which  they  used  aluminum  hydroxide  as 
the  clarifying  agent  in  lactose  determinations.  The  reagent  was 
made  hy  precipitating  aluminum  hydroxide  from  a solution  of 
ammonium  alum  with  ammonium  hydroxide  and  washing  hy  decantation 
till  pure.  The  aluminum  hydroxide  was  finally  centrifuged  and 
the  thick  jelly  obtained  made  somewhat  thinner  hy  agitation  with 
w'atar.  In  using  this  reagent  the  authors  obtained  results  very 
close  to  those  obtained  hy  the  copper-alkali  method  and  the  fil- 
tration was  much  easier.  ija  excess  of  reagent  does  not  influence 
the  results  whatever. 


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8 


- KICPZ13II.IElTT;ji  - 


In  this  investigation  the  samples  of  milk,  all  of 
which  were  very  kindly  furnished  hy  the  dairy  department  of  the 
College  of  Agriculture  at  this  University,  v;ere  first  analysed  hy 
the  official  optical  Q.  A.  0.  method,  mercuric  nitrate  heing 
used  as  the  precipitant.  The  result  hy  this  method  w:,s  used  as 
a guide  for  tue  other  methods  tried  us  this  has  keen  accepted  as 
a standard. 

The  reagent  v;as  prepared  ky  dissolving  mercury  in 
dcukle  its  weight  of  nitric  acid,  (sp.gr,  1,42}  aaid  diluting  with 


. volume 

of  distil 

led 

water. 

For  the  amount 

of  milk 

CG. 

was 

found  to 

ke  £ 

iufficient  to  furnish 

an 

ezeess. 

'ity 

of  milk 

to  ke 

used  varies 

with  the  sp( 

3Cific  gravitjr 

the 

type  of 

polar 

iscc 

p3  used. 

Sp. 

gr. 

of  L 

a Ik 

Ycl. 

of  milk  to 

ke 

used 

for 

pol arise ope 

whose  sucrose 

nom 

lal  weight  is  26.048  grams, 

1. 

024 

• • 

• 

. . 

64,4  cc. 

1. 

026 

• 

• 

• . 

64.3 

1. 

028 

• 

• 

• • 

64.15 

1. 

030 

• 

• 

• • 

64.00 

1. 

032 

• • 

• 

• . 

63. 90 

1. 

034 

• 

• 

• . 

63.80 

1. 

035 

• 

• 

• . 

63.70 

The 

qua 

ntit 

y of  milk 

indicated  is  placed 

in 

a flask 

at 

102. 

6 cc 

. for 

a Yi 

antsiia,  o 

r 102.4  for , 

a n 

aurent  po- 

• 

8.5 

GG. 

acid 

mer< 

eurio  nit 

rate  and  3.5 

cc 

. alumina 

a 


wim 


\ 


iLk  « 


9 


crGon,  to  help  in  tho  clari fioati on  are  adcled.  The  Hack  is 
filled  to  tl]e  nark  ";ith  distilled  water,  a£;itated,  filtered 
through  a dr;^  filter  and  polarised.  TThen  using  a 200  nm.  tube 
the  reading  is  to  he  divided  hy  2 if  the  sucrose  normal  weight  is 
26.048. 

The  optical  method  was  also  studied,  anhydrous  basic 
lead  acetate  being  used  as  the  clarifying  agent  in  this  method. 
2-3  grams  of  this  salt  was  sifted  into  the  flask  containing  the 
milk  and  3 cc.  of  alumina  cream  a.dded.  The  flask  was  then  filled 
to  the  mark  with  distilled  water,  filtered  through  a dry  filter 
and  polarized  the  sanie  as  in  the  preceding  method. 

In  the  gra,vimetric  n.  0.  A.  G. , 25  cc.  of  milk  is  di- 
luted in  a 500  cc.  flask  to  400  cc.  with  distilled  water  and 
10  cc.  of  a Solution  of  copper  sulphate  added,  this. copper  sul- 
phate of  the  strength  given  for  Soxhlet*s  modification  of  the 
Pehlings  solution,  which  is  69.378  grams  of  OuS04*5  FgG  in  one 
liter.  About  7.5  cc.  of  a solution  of  potassium  hydroxide  is 
added  of  such  strength  that  one  volume  of  it  is  just  sufficient 
to  completely  ]precipitate  the  copper  as  hj'drcxide  from  one  volume 
of  the  solution  of  copper  sulphate.  Instead  of  potassium 
hydroxide  8.8  cc.  of  half  normal  sodium  hydroxide  nay  be  used. 
After  the  addition  of  the  alkali  solution  the  mixture  must  still 
have  an  acid  reaction  and  contann  copper  in  solution.  The  flask 
is  filled  to  the  500  cc.  mark,  agitated  and  the  solution  filtered 
on  a dry  filter. 

In  this  filtrate  the  la-ctcse  is  determined  by  copper 
reduction  method.  50  cc.  of  mixed  copper  I'ehlings  reagent  is 
placed  in  a beaker  and  heated  to  the  boiling  point.  7hile 


u 


f . ‘ ^ 

x » • * r 


0 .; 


ti,  ^ 


m 


r:a 


I* 


1 


’ f <4.4 


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t 


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;•*  .^^.v  Hv  , ]-  ,vjt. 


-J* 


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1.;^  i*  y ?-'.i' 


' a 


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' 1 I * - 


. •'  ♦ I ^ ••  T . . 

%'4  • 


■ T. 


. Ij  Jl  ^ 


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..t  i / 


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^ i ' • .Wa 


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, r, 

, ' *■  'ri 

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/il  Is  1 1 .,  !_• 

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; 1 

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! I , 'J  Jiitt  jii  tf!  . J : I . ^0^  M . .*  Jli<  I - il 


■<r  ■ '•<<.£!■! 


10 


TDoiling  iDrislily,  100  gq.  of  the  lactose  scliiticn  is  added  and 
"boiled  for  six  minutes,  immediately  filtered  through  an  asbestos 
Gooch  crucible  and  washed  with  hot  water,  10  cc.  ethyl  alcohol, 
o-nd  10  cc.  ethyl  ether.  The  precipitate  is  dried  at  lOO^’O.  and 
weighed  as  cuprous  oxide.  The  percentage  of  lactose  is  calcu- 
lated from  the  Soxhlet  and  TTein  table  for  lactose. 

The  chief  difficulties  in  the  gravimetric  method  here- 
tofore have  been  the  very  slow  fil.tration,  and  the  acid  concen- 
tra.tion  of  the  solution  to  effect  good  precipitation.  The 
author  has  attempted  to  overcome  these  difficulties  in  this  worlr. 
The  procedure  of  the  A.  L.  C.  was  somewhat  modified  \Tith  this 
in  view. 


In  a 500  cc.  flasli,  25  cc.  fo  milk  are  placed  and  di- 
luted to  400  cc.  with  distilled  Water  and  10  cc.  of  copper  sul- 
phate solution  added  of  the  strength  used  in  the  x*.  C.  A.  0. 
method.  Then  2 or  3 drops  of  phenolphthalein  are  added  as  in- 
dicator. Half  normal  sodium  hydroxide  is  dropped  in  slowly  till 
the  solution  is  left  just  barely  acid.  If  the  end  point  is 
over-run  slightly  it  is  brought  back  with  a few  drops  of  dilute 
sulphuric  acid  without  seeming  to  effect  the  results  in  any  way. 
The  solution  is  diluted  to  500  cc.  and  shalcen  well.  Part  of 
this  solution  is  next  transfered  to  a SOO  cc.  centrifuge  bottle 
and  whirled  in  a centrifugal  machine  for  20  - 30  minutes  at  about 
800  R.  P.  11.  At  the  end  of  this  tim.e  the  precipitate  is  q.uite 
tightly  packed  in  the  bottom  leaving  an  almost  clesji  supernatant 
liquid.  This  supernatant  liquid  is  then  run  through  a diy 
filter  and  the  resulting  filtrate  used  in  method  explained  above. 

It  w'as  a,lso  found  that  this  filtrate  could  be  quite 


11 


easily  polarized  just  as  when  acid  mercuric  nitrate  is  used  as  a 
clarifying  agent.  The  copper  left  in  solution  after  treating 
hy  this  procedure  is  of  such  a small  ausntity  as  not  to  color 
solution  sufficiently  to  prevent  reading  of  the  polariscope. 


1-2 

-LATA- 

SAI'.-IL3 

- ■ ■ ■ 

— 

' " 

imxBSH 

I 

- - 

II 

III 

lY 

Y 

YI 

Specific 

1.032 

Gravity 

1.030 

1.0304 

1.0354 

1.0308 

1.028 

1 

HgdTOgjg 

9.05 

9.05 

9.67 

9.24 

9.84 

9.34 

( reading) 

9.27 

9.09 

9.65 

9.32 

9.20 

1 9.50 

percent 

4.525 

4.525 

4.835 

4.62 

4.85 

4.67 

Lactose 

4.58 

4.635 

4.535 
4 , 54& 

4.83 
4^025-  - 

4.64 

4.66  . - 

4.76  • 
1 4,a7 

4.71* 

-4.75- 

Anhydrous 

8.22 

8.04 

8.42 

8.82 

8.36 

sample 

lead  acetate 
(reading) 

8.34 

7.94 

8.22 

9.06 

8.60 

lost 

Percent 

4.11 

4.02 

4.21 

4.41 

4.18 

4.14 

3.995 

4.16 

4.47 

4.24* 

Lactose 

. — _ 

^4.17 

3.97 

. 4.11  __ 

4.53 

4.30 

Clarified  with 

copper  sulphate  and  sodium 

hydroxide 

optical 

. 69 

.68 

.744 

.719 

.721 

Headings 

.71 

.69 

.741 

.705 

.736 

.720 

Percent 

4.416 

4.363 

4.752 

4.55 

4.615 

4.613 

4.445 

4.392 

4.74 

4.531 

4.67 

4.607* 

Lactose 

4.473 

4.421 

4.728 

4.512 

4.725 

; 4.601 

Height 

■ 

.3750 

.3676 

. 3934 

.3857 

.3770 

.3761 

CugO 

.3741 

.3728 

.3971 

.3722 

.3961 

' .3891 

Height 

. 2996 

.2928 

.3139 

.3079 

.3080 

; . 3008 

Gu 

. 2989 

.2972 

.3164 

.2969 

.3161 

.3102 

percent 

4.48 

4.391 

4.698 

4.61 

4.615 

14.512 

4.475 

4.42 

4.728 

4.528 

4.681 

1 4.58^^ 

Lactose 

4.47 

4.449 

4.758 

4.446 

4.747 

!4.648 

* Averages. 

13 


- DISCUSSICII  - 

!Prom  the  tahles  of  data  it  can  "be  seen  that  the  results  ^ 
secured  hy  the  use  of  hasic  lead  acetate  were  rather  unsatisfac- 
tory. HcVifeYer,  this  was  to  he  eir-.ected  since  this  i:)rocedure  has 
never  appeared  to  give  satisfactory  results  with  other  investi- 
gators. ihe  quantities  indicated  hy  this  method  were  all  con- 
siderably lower  than  those  obtained  by  using  mercuric  nitrate. 

Vary  good  check  results  were  obtained  by  using' the 
modified  copper  sulphate  clarification  procedure.  lha  percen- 
ta,ges  of  the  gravimetric  method  and  the  polarimetric  determination 
check  vary  closely  with  each  other  although  they  are  about  one 
tenth  of  one  percent  lower  than  the  results  of  the  A.  g.  A.  G. 
method.  These  may  be  low  due  to  not  having  complete  precipita- 
tion of  the  dextro-rotatory  nitrogen  compounds  when  acid  mercux'ic 
nitrate  was  used  for  this  purpose. 


"•i 


^1-. 


' U ^ 


- a.* ;^: , |, i«6:  '*ii'i ' ^iV'l  Q J ,,i  j 4-1  ^ ^ r^’ ^ W ' >'  . 


■?) . 
r 


' .,'  * . ,’^ri''''  “.  •;,  j ■.€»■•  »» 

U'^(l  stdi-Vy^'i^  ■ -4  ''  's/iao 

^ 1 ■ ' . (V  ' V ' * ^ ^ 

,.  i,'  „ k'  1*1  i‘  n'^'  j"  'i-  .„,  . 


- i ) ^i'  y /■i|l',.?i  >'>-^i  ■ v',  i , ‘.  ;‘  (tn  ■ ■ '•<; 'c>Af  ;in 

'■'  j ■%.  ' "I  - k.  I.**  ■'  '■  ‘ V ' V' 

: ' "^  "'  i,  . 1 A',*: 

,“■  i[  ''-i  A>iki'i’A'  S’4‘''^  ‘/ui'  iv’  ■ii/nS' , ", 


"fe-V-lt 'I 

,'  . : .' :5Hf  jisiE;  v.Miiifci:  '1 


'r^A'  ‘"f  ';■!<«*• 

rv,>-'-  mm 


r.';„,By’_  ..- , '.l  'iJ,,:tmS  ■aSui*' ...»a«  : . 


*v  -•>■ 

I . X I .y. 


a ;:  ,,•.  *.'r ■:•« 


,. ..  , „ ,, ,_, 
4 . ’ I ' I , ’ V *tfj-  . •.I'  .1^'  f .. ' / 'li ' - 

’ , ,,.\''r^f*  ■ , '^  Wr  '' 


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: ' ' : -;>Sr^f0^W  ^ 


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{':''  ■ Aji'f''’ '•#•'*; ■': ' '. 

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jp  , *..  • ■•'.  vi'f' !■.■■•.  . • 
i»r4  ’■. ' I’:". 


14 


-SUMHART- 

1.  This  study  was  undertaken  with  the  ohjeot  of 
determining  a more  efficient  method  of  adjusting  the  acid 
concentration  of  solutions  of  lactose  after  clarification 
with  copper  sulphate,  and  ox  determining  a more  rapid 
method  of  filtration.  These  have  heretofore  heen  the 
chief  difficulties  in  lactose  determinations.  The  diffi- 
culty of  acid  concentration  is  easily  overcome  "by  using 
phenolphtha-lein  as  an  indicator. 

S,  The  inability  to  secure  a rapid  filtration 
after  the  clarification  has  been  eliminated  bj^  centri- 
fuging the  solution  before  attempting  filtration.  The 
supematsjit  liquid  is  then  verj-  easily  filtered. 


'^4 


...Ci  ■'  • 


^'1 


Wfc'if^ffF^  ^1*.  ■•-^* 

™ ' ‘ ' I " -I k ■' ' " ■ • - t fi 

iV  V ?)  “-  I - K^W 


j>  i) 


^sL  **J 


*J. 

,,;|^VV^'.^; 

■ ■ : , ’ 4%  i.0*4'* . f;  mmM&k 


'y\ 


i'*J5sK 


■'• ' ■ ■ '■'®: . ■■'  ^'7^'"'  ‘ 7^JW^’' »«» ' ■ « 


Ui. 


* >»- 


- .»j  , 

■r*TS"*^j 


Si  :Lj  y ■ >' ^-ji^*!:.' ,>jM)l||^  ‘ ■'•  i^^K|Q| 

i'*>  ‘*i  *'  :^Jifefi8c,“>''.'  ' 'iJM-  Bit  ^ “hB 


•fi<M  ' , ^»^.y  i'  '•  m 

‘.V 


- B I B L I C 

G H A P H 

r ^ 

1. 

iim.  Gharn.  Jour. 

• . 6 : 

289 

(1884) 

2. 

Analyst 

. . 5: 

35 

(1880) 

3. 

Analyst  . 

. . 8 ; 

243 

(1883) 

4. 

Analyst 

9: 

116 

(1884) 

5. 

xinalyst 

. 10: 

62 

(1885) 

6» 

ilnalyst 

. 11: 

28; 

141  (1886) 

7. 

iinalyst 

12: 

176 

(1887) 

8. 

Analyst 

13: 

63 

(1888) 

9. 

xinalys  t 

. 20: 

121 

(1895) 

• 

o 

H 

iinalyst 

21: 

162 

(1896) 

11. 

Analyst  . 

22: 

98 

(1897) 

12. 

iinalyst 

. 26 : 

127 

(1901) 

13. 

imalyst 

. 35: 

516 

(1910) 

14. 

Bulla  tin  107  U.  S. 

Gbernistr^:" 

Bureau 

15. 

Jour,  of  iiX-i*  Gbem. 

See.  15: 

694 

(1893) 

16. 

Jour,  of  iijfl.  Giaem. 

SoG.  35: 

823 

(1913) 

